Comparison of high and low voltage-rays: No wave-length effect was demonstrated when either 124-kv, 2-Mev, or 50-Mev x-rays were similarly distributed through various test organisms. No effect of neutron production on cataract formation was exhibited by 50-Mev x-rays. Induced radioactive O, N, and C, unless exhibiting unique biological effects, was considered an insignificant part of the total radiation (0.005 in 3050 r). A marked difference in survival times was shown by a comparison of 124-kv or 200-kv and 50-Mev x-rays. Radiation genetics of the parasitic wasp: X-ray (200 kv)-induced recessive lethals in first meiotic metaphase eggs were studied. For those eggs treated with 500 r (LD sub-60 dose), the rate was about 5% as compared to 7% for prophase eggs treated with 12,000 r (LD sub-50 dose). It appeared that recessive lethal rates can be secured for 3 gametic stages. Biochemical activities of x-ray induced yeast mutations: Studies were initiated on mutant 46 Y, which is unable to utilize atmospheric O, to determine the character of the physiological block. Dyes ranging from Eo' (pH 7.0) 0.06 to -0.3 and tripeptide glutathione were employed to test the hypothesis that O utilization might be restored by a substitute redox system; inconclusive results appeared to indicate that such a system may act to bridge the gap between 1 enzyme system and another.